1. Field of the Invention
This invention relates to a polymer composition having an improved degree of dispersibility and solubility in water.
More particularly, it is concerned with an easily dispersible composition for water soluble polymer which comprises a powder of a water soluble polymer having coagulating or flocculating property and a hydrated sodium sulfate, and if required hydrated magnesium sulfate and/or a hygroscopic agent.
2. Description of the Prior Art
A water-soluble polymer having flocculating property is useful as a flocculant, aid for dehydration, or the like. It is used as an aqueous solution having a polymer content of, say, 0.1 to 1.0% by weight which is usually prepared in a tank. This aqueous solution is prepared by dissolving a polymer powder in fresh water each time it is needed, but there are not a few cases in which additional quantities of the polymer powder and water are supplied into the tank for preparing an additional supply of the solution when the tank still contains some solution which has previously been prepared, depending on the shape of the apparatus and the convenience of the work. When it is desired to prepare a large quantity of any such solution, however, there is every likelihood that the polymer powder may hardly be dissolved in water even if stirring is continued for a long time. (Because the polymer powder, when put into water, gets wet on its surface before dispersing, absorbs water and forms a gelatinous coat of the surface, which adheres each others and becomes a large mass.) This is particularly the case when the solution is prepared in a tank which holds some previously prepared solution. As the remaining solution has an increased degree of viscosity, a longer period of stirring is required for dissolving the polymer in water.
In order to solve these problems, it has been proposed to coat the surfaces of the polymer particles with a polyhydric alcohol, glycerol, or the like, or admix a mineral or vegetable oil, or the like into the polymer. It has also been proposed to prepare a composition by mixing the powder of a polymer with a powdered acid such as oxalic acid or tartaric acid, or a powdered base capable of foaming upon reaction with any such acid, so that the resulting foams may be utilized for preventing cohesion of the polymer particles physically while they are still in the `wet` condition (Japanese Patent Application Laid-Open No. 61636/78). Recently, it has been disclosed in Japanese Patent Application Laid-Open No. 28612/81 that a powdered composition for flocculant is obtained by mixing a polyacrylamide and calcium chloride dihydrate with water in an amount which is sufficient to mix the former two components but is less than the amount to be maintained in the molecule of calcium chloride. However, such compositions show disadvantages such as less storage stability and lack of free-fluidity. None of these proposals has, however, been fully satisfactory from the technical or economical stand-point.
Further, the inventors of this invention have proposed an easily dispersible composition comprising a water soluble polymer, an alkali metal hydrogensulfate and a basic inorganic salt such as dipotassium hydrogenphosphate (Japanese Patent Application No. 160569/1974, U.S. patent application Ser. No. 274,437, German Patent Application No. P3123922.6).